What does 1 Samuel 17:29 mean?

David's oldest brother is furious with him. Eliab has lashed out at David to try to put the younger man in his place (1 Samuel 17:28). David has only just arrived at the battle front of Israel's standoff with the Philistines (1 Samuel 17:1–3, 19) as a delivery boy (1 Samuel 17:17–18). David has heard the taunts of the Philistine champion (1 Samuel 17:23), which Eliab and Israel's army have endured for over a month (1 Samuel 17:16). No one from Israel's army has volunteered to fight the huge warrior (1 Samuel 17:4–10), despite the promise of a substantial reward from the king (1 Samuel 17:25). Neither have King Saul nor his heroic son Jonathan stepped up to take on Goliath. The fight seems unwinnable and the Israelites are terrified (1 Samuel 17:11, 24).

But when David hears the threat, he asks what will be done for the man who kills Goliath (1 Samuel 17:27). He highlights the shameful situation Israel's army is in. He also wonders who this Philistine thinks he is to challenge the armies of the living God. The godless man is no match for the God of Israel. Is Eliab's kid brother really suggesting that he could possibly defeat the champion of the Philistines in one-on-one combat? Eliab has called David a presumptuous thrill-seeker who has only come to be close to the excitement of battle (1 Samuel 17:28).

Now David responds as younger siblings have done throughout earth's history, "What have I done now?" David asks something like "wasn't it just a word?" Commentators disagree on the meaning behind this statement. Some understand David to be saying something like, "I was just asking" or "Can't I even talk?" Others think the youthful David is insisting that he is asking about something important and genuinely wanted to understand.